1. Field of the Invention
This invention relates to a stereoscopic X-ray apparatus for irradiating X-rays from right and left portions in two directions to intersect at a to-be-examined object by using a stereoscopic X-ray tube or the like and using X-ray images obtained in the above two directions so as to permit the object to be stereoscopically observed.
2. Description of the Related Art
As an example of a conventional stereoscopic X-ray apparatus, an X-ray apparatus is known in which X-rays are sequentially irradiated from two foci of a stereoscopic X-ray tube and two X-ray images obtained by two X-ray irradiations are photographed on two X-ray films. The X-ray films after being subjected to development are placed side by side on a film viewer and the object may be stereoscopically observed by using the parallax between the two images.
In recent years, digital fluorography is widely used, and in this case, an X-ray image having passed an object to be examined is picked up by means of an image intensifier tube and TV camera and picked-up images created by X-rays from the right and left foci are stored into an image memory. Then, the picked-up images created by X-rays from the right and left foci and read out from the image memory are displayed on two display units. Also, in this case, the object can be stereoscopically observed in the same manner as in the case of using the films. The stereoscopic display method in the digital fluorography includes a dynamic stereoscopic display method which requires use of field switcher glasses with electronic shutters and in which right and left images are alternately displayed on a single display unit and the electronic shutters are alternately driven in synchronism with alternate display of the images in addition to a static stereoscopic display method in which two images are simultaneously displayed on the two display units as described above.
In the above conventional cases, since the stereoscopy is determined by the parallax between the images, it can be determined by a distance between the foci of the stereoscopic X-ray tube, which is generally a fixed value, a distance between the image intensifier tube (or film) and the X-ray tube, and a distance between the image intensifier tube (or film) and the object. The latter two distances change according to the image pick-up condition (geometrical relation among the X-ray tube, object, and image intensifier tube). Therefore, the stereoscopy is determined by the image pick-up condition and it will be changed according to the image pick-up condition. Further, since the sensitivity to the stereoscopy may be different for different persons, it sometimes happen that the stereoscopy of the same stereoscopic display image is sufficiently high for one person but may be low for another. In this case, if the stereoscopy is low, the positional relation in the depth direction between two things may be erroneously recognized.